Glucocorticoids (GCs) are a class of steroid hormones that bind to and activate the glucocorticoid receptor (GR), which is present in almost every vertebrate cell. The GR is pleiotropic and regulates a variety of important pathways in the vertebrate organism, for example, metabolism, immunity, and development. As such, detection of GR activity or regulation can be used to diagnose a variety of different vertebrate diseases, or assess a clinical or biochemical response to treatments that modulate GR activity.
For example, detection of GR activity or regulation can be used for detection of various forms of Cushing's syndrome. As another example, glucocorticoid receptor antagonists (GRAs) can be administered to a patient to treat a number of different diseases and conditions, and detection of a change in GR activity in response to administration of the GRA can indicate or assess a clinical or biochemical response to the treatment. However, current methods and compositions for assessing GR activity suffer from one or more of the following insufficiencies: high cost, low sensitivity, low specificity, high false positive rate, or high false negative rate. Therefore, there remains a need for improved methods and compositions for detection of GR activity.